Insulator



May 5, 1936- P. A. WICKMANN INSULATOR File d Jan. 19, 1935 INVENTOR PM;415597 ,Mm mn A/ A ORNEY Patented May 5, 193a" UNITED STATES PATENT.OFFlC 7 msum'ron poration of V Application January 19, 1935, Serial No.2,543

Claims.

This invention relates in general to thermal insulators and, inparticular, to an insulator against visible and infra-red radiation. The

thermal radiation and against heat derived therefrom.

It is another object of the invention to provide, as an article ofmanufacture, an insulator against light and/or thermal radiation comprising an element having a low thermal conductivity and another elementhaving a high reflectivity for light and thermal radiation.

It is a further specific object to provide an insulator against lightand thermal radiation characterized by being thin, flexible, light inweight and economical to produce and having a metal reflecting surfacewhich is capable of following the changes in dimensions of the base andwhich can be bent and flexed without cracking.

It is a specific object of the invention to provide fibrous insulatingmaterials having a porous and rough surface with a non-porous and smoothsurface and thereafter to deposit on the prepared surface an extremelythin coating of metal having a high reflectivity for light and thermalradiation.

A further specific object of the invention is to provide an insulatingsheet which is moistureproof, greaseproof, air and light proof, andcapable of being fashioned into containers or used as a wrapper for theprotection of articles from the effects of changes in the atmosphericconditions surrounding them. v

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises an article of manufacture possessingthe features, properties and the relation of elements which will beexemplified in the article hereinafter described and the scope of theinvention will be indicated in the claims.

According to the invention, an article having high reflectivity forlight and thermal'radiation and high insulation values is formed bydepositing on one or both sides of a sheet of material having a. lowthermal conductivity, a multiplicity of fine particles of metal in theform of a layer having the appearance of a smooth, continuous coatingand having a thickness of not substantially greater than .0002 of aninch. The deposit of metal employed in this invention is more properlydescribed as a coating than as a metal fllm and distinguishes overthelatter in being heterogeneous in structure and hence capable offollowing the expansion, contraction and wrinkling of the base withoutcracking or flaking oil, and in being strongly adherent to the basewithout the use of an adhesive. In particular, the metal coating of theinvention is especially adapted for water-swelling colloids such asregenerated cellulose, gelatine, casein, alkali-soluble cellulose etherswhich bases are subject to changes in dimensions due to changes in theatmospheric conditions.

In its preferred embodiment, the backing consists of a flexible sheet offllm of a non-fibrous organic plastic material such as regeneratedcellulose, cellulose derivatives, gelatine, casein, or other syntheticor natural plastics, or a composite sheet formed, in whole or in part,of one or more of such materials.

The reflecting surface deposit may be formed of any suitable metal whichis characterized by affording a substantial degree of reflectivity forthermal radiation, which has preferably a relatively low thermalconductivity and which is, in addition, capable of being deposited inthe form of particles of atomic dimensions to give the appearance of acontinuous coating having a smooth surface of high lustre. Suitablemetals for the preparation of this coating include silver, gold,platinum, chromium, tin, and other heavy metals as well as alloysthereof. 1

By way of illustration, but not limiting the scope ofthe invention, thethin coating of metal may be deposited upon the backing material bycathode sputtering from suitable electrodes. For example, exceedinglythin coatings of silver and other metals may be deposited on the basematerial by cathode disintegration of heated metal electrodes having athickness of from A, to 3 times the length of the main free path, atworkin pressure, of the atoms formed by the disintegration of thecathode.

It is to be understood, however, that the present invention contemplatesthe use of thin layers of metal particles produced in any suitablemanner such, for example, as by the deposition of metal from a solution,as by electrodeposition or chemical deposition, or by a cathodedisintegration process other than that above disclosed. The coating ofmetal may be formed by evaporating a suitable metal and condensing themetal vapor on the surface of the base material. In all of theseprocesses, the disintegrated metal, in the form of particles of atomicdimensions, is deposited as a thinlayer having a granular discontinuousstructure, pearance of a continuous coating. The coating of metal has apreferred thickness of .0001 of an inch but may have a thickness up to.0002 of an inch.

For a more complete understanding of the nature and objects of theinvention, reference should be had to the following detailed descriptiontaken in connection with the accompanying drawing, in which:

Fig. 1 is a sectional view of a simple modification of the novelinsulator of the present inven-- tion comprising a single backingelement and a single reflecting coating.

Fig. 2 is a sectional view of a further modiflcation, of the improvedinsulator comprising a single backing element carrying a reflectingcoating on both sides.

Fig. 3 illustrates a sectional view of a modification of the novelinsulator in which there is provided a plurality of backing elements anda plurality of reflecting coatings in alternate layers.

Fig. 4 illustrates a sectional view of a modiflcation of the novelinsulator which comprises a plurality of backing elements carryingreflecting coatings on opposing sides.

Fig. 5 illustrates a sectional view of a modiflcation of the insulatorof Fig. 4 in which an air film is provided between the opposingreflecting coatings.

Fig. 6 illustrates a sectional view of an embodiment of the presentinsulator in which the reflecting coating is provided with a hem.

Fig. '1 is a sectional view of an insulator of this invention providedwith an edge-reinforcing element.

Fig. 8 is a sectional view of the insulator of Fig. 1 after it has beenmodified by embossing or the like.

Fig. 9 is a sectional view of an insulator in which the base sheet hasbeen given a preliminary surface coating before the deposition of themetal coating.

Fig. 10 is a sectional view of an insulator which has been provided witha transparent coating over the base and the reflecting coating.

Fig. 11 is a view in perspective of an insulatin unit comprising aplurality of sheets of the novel insulator of the invention.

Referring now to Fig. 1, the present invention consists in a simpleembodiment of a single flexible sheet i of backing material of the classdescribed carrying on one surface a thin coating 2 of metal particleshaving a high reflectivity for light and/or thermal radiation and havinga smooth surface of high lustre. Alternatively, as shown in Fig. 2, bothsurfaces of the backing i may carry a thin coating 2 of metal having ahigh reflectivity for thermal radiation. For some purposes a pluralityof such insulator sheets may be used with advantage. In such cases, themetal coatings of the two adjacent insulator sheets may face in the samedirection, as shown in Fig. 3, or the metal coatings may contact eachother on opposing faces, as illustrated in Fig. 4.

Further, it has been found that the degree of insulation is materiallyincreased by separating the adjacent sheets by an air film. The air filmmay be provided either when the metal coatings are facing in the samedirection or when the metal coatings face each other. In Fig. 5 there isillustrated a simple embodiment of this mod but giving the visible apthenovel insulator of iflcati'on of the invention in whichtwo sheetsof thesame dimensions, each comprising a flexible sheet of non-metallicmaterial. I having a thin coating of metal 2 are united throughout areasadjacent the edges thereof by'a layer of a suitable adhesive, theremaining areas of the opposing faces being free of adhesive so that anair fllm 4 is provided between them. It will be apparent that if onedesires to increase the crosssectional area of the air film a spacerstrip 3 of some suitable material such, for example, as

wood, metal or plastic, coated on both sides with a suitable adhesive,maybe disposed between the sheets.

In certain applications of the novel insulator of this invention; aswill be hereinafter further described, it is advisable to provide theinsulator sheet with means to resist tearing at the edges. For instance,a suitable means of reinforcing the edges may comprise a hem 5 formed byfolding over the edge of the material as shown in Fig. 6. In thismodification of the invention, the metal coating need not be depositedover that portion of the material which is to comprise the hem. Or, asan alternative, an extraneous material, preferably of low thermalconductivity, in the form of a narrow strip or band 6 of paper, fabricand the like may be folded about and secured to the edges of theinsulator sheet, as illustrated in Fig. '7.

In accordance with the practice which has' been found desirable forcertain purposes in in sulation engineering, the insulator sheet may begiven a plastic alteration of its surface such, for

example, as by passing the sheet through a pair of embossing rollers toproduce a sheet having surface irregularities, as illustrated in sectionin Fi 8.

When the base of the insulator is a porous flbrous material, such, forexample, as paper, flber board, asbestos, felt, fabric, leather, thebase is preferably first treated or coated with a suitable film-formingmaterial or composition to impart to the base a non-porous, smoothintermediate surface coating 1 upon which the metal coating 2 isdeposited, as shown in Fig. 9. Suitable intermediate coatings may beformed from synthetic or natural gums or "resins, drying oils,varnishes, cellulose derivative lacquers, gelatine, casein and otherfilm-forming substances. These substances may be applied to the base bycoating it in a known manner witha solution of one or more of thecoating materials in a suitable solvent. If desired, plasticizers,pigments, waxes, etc., may be added to the film-forming substance toimpart flexibility, color, moisture resistance, etc., respectively.

The functions of the intermediate coating are, among others, to renderthe base non-porous and smooth so as to impart a corresponding smoothsurface to the metal coating; to enable a continuouscoating of metal tobe produced with the minimum amount of metal thus eflecting a saving inthe coat of the insulator; to strengthen the backing; to prevent theformation of cracks in the metal coating when the base is bent orflexed; andto increase the adherence of the metal particles to thefibrous materials. It is to be understood, however, that non-fibrousbase material may be given a preliminary coating if desired although apreliminary coating or an adhesive layer is not necessary to secureadherence of the metal particles to such material.

To protect the thin, fragile coating of metal containing a cellulosederivative, a plasticizer.

oxygen, sulphur or other agents, the metal coating may be covered with athin over-coatings, as shown in Fig. 10. The over-coating should be onewhich is free of ingredients having a tendency to discolor upon exposureto visible and infra-red radiation and it should be inert with respectto the underlying metal. A suitable material for this purpose comprisesa transparent, preferably moistureproof, film-forming substance orcomposition such, for example, as a lacquer and a wax; a varnishcontaining a synthetic or natural resin, a plasticizer and a wax; aswell as compatible mixtures of chlorinated dlphenyl, chlorinated rubber,polymerized vinyl compounds, with or without plasticizers, sum orresins, and wastes. A moistureprooi overcoating on both sides of theinsulator is especially adv'an tageous where the base sheet I consistsof a water-swelling colloid such as regenerated cellulose, gelatin,casein and alkali-soluble cellulose ethers, since the coating not onlyprevents the tarnishing of the metal deposit 2, but also prevents thedistortion of the base with change in the atmospheric humidity.

In-Fig. ll there is illustrated one modification of a multi-plyinsulator oi the invention, in which the sheets of insulator arearranged in parallel and aflixed at opposing ends by a clamping device 9provided with slots ill in which the edges of the sheet are embedded anda. bolt or screw H by which the block may be compressed so as to holdthe sheets within the slots. It is immaterial what exact form this unitmay take but it is preferable to separate the insulator sheets by spacesof suitable dimensions so as to provide alternate layers of insulatorand layers of air or gas. If such insulating units be incorporatedwithin the walls of vehicles, a substantial insulation against thermalradiation is provided.

Further, for some purposes, it has been found advantageous to color thebacking sheet with a substance capable of absorbing light transmitted bythe metal coating. The insulator is thus rendered more or less opaque inthe particular region of the spectrum absorbed by the article or inwhich region the metal film is more or less transparent. For example, ared dye may be used to render the backing substantially opaque to thematerial with a red backing would be advantageous for protecting foods,the skin, etc., from the efiects of the more active blue light, forwhich light some metals, such for example as silver, are more or lesstransparent.

The novel insulator provided by this invention is especially applicablefor use in protecting various objects, articles, containers and chambersagainst the effects of visible and infra-red radiation and against theheat derived therefrom. The applications of the novel insulator of thein: vention may be illustrated by the following examples.

The flexible insulating sheet herein provided may be employed as awrapping material for fruits, dyed textiles, tobacco products, softdrinks, wines, champagnes and other materials, and objects which it isdesired to protect against the effects of visible and infra-redradiation. The insulator sheet herein described may be employed as onemember of a blank for boxes, cartons, bags, trunks (especially for thetropics), and other formed containers for preserving foods such, forexample, as candy, butter, cheese, vegetables, and industrial productssuch, for example, as soapand the like.' Further, it may be em; ployedas an inner lining for hats, such, for we ample, as tropical helmets,andlumbrellas for use on the beach, porch, garden, street, and for lin-'in'gsor partial linings for clothes, dresses; for window protection, inthe form of shades, awnings, curtains; book covers, lamp shades, flrescreens and other objects or articles which it is desired to insulateagainst thermal radiation.

The novel article of this invention may be employed'as an insulatorforthermos or Dewar flasks of the double-wall types. In such installations,it is preferably incorporated intermediate the double walls of thecontainer.

Ithas long. been desired to insulate chambers in refrigerators and invehicles, such, for example, as automobiles, railroad cars,.airplanes,ship's cabins, etc., against .the heat derived from exposure to the sunand from motors, burners, etc. The insulator of this invention isparticularly adapted for use as an insulating medium for such vehicles.

When the article of this invention is used for insulating movingvehicles, it will be found that regenerated cellulose is admirablysuitable for use as the flexible sheet of non-metallic material formingthe backing,'as such material has a high tensile strength and tends toshrink when heated, so that the sheets will remain taut within the frameor support. In view thereof, there is little danger of adjacent sheetscrumpling and contasting each other as is the case with the unbackedmetal foils heretofore used as insulators for vehicles.

It is observed that the present invention provides a novel and usefulinsulator having many advantages over prior insulating materials. Thebacking element of the present insulator is characterized by having arelatively low thermal conductivity. This property decreases thequantity of heat transmitted under given conditions as compared to aself-sustaining metal foil. The other member of the novel combinationconsists of a metal coating characterized by extreme thinness and asmooth surface having a high lustre. This latter characteristic resultsin the coating being an excellent reflector of visible and infraredradiation.

While the present invention has been described with some degree ofexactness and detail, it is to be understood that the invention is notlimited to such detail, but inasmuch as certain changes may be made inthe above article and different embodiments of the invention could bemade without departing from the scope thereof, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

Having described my invention, what I claim as new and desire-to secureby Letters Patent is:

1. As an article of manufacture,.an insulator against light and thermalradiation comprising a sheet formed of a non-fibrous, organic, plasticmaterial and having on its surface a multiplicity of particles of metalof atomic dimensions deposited in a layer having a granular structure,but giving the visible appearance of a continuous, lustrous coating,said layer of metal particles having the property of following theexpansion, contraction and wrinkling of the sheet material withoutcracking or flaking oil.

2. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of a non-fibrous, organic, plasticmaterial swelling in water and having on its surface a multiplicity ofparticles of metal of atomic dimensions deposited in a layer having agranular structure. but giving the visible appearance of a continuous,lustrous coating, said layer of metal particles having the property offollowing the expansion, contraction and wrinkling of the sheet materialwithout cracking or flaking oil.

3. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of a nonfibrous, cellulosic materialand having on its surface a multiplicity of particles of metal of atomicdimensions deposited in a layer having a granular structure, but givingthe visible appearance of a continuous, lustrous coating, said layer ofmetal particles having the property of following the expansion,contraction and wrinkling of the sheet material without cracking orflaking off. 4. As an article of manufacture, an insulator against lightand thermal radiation comprising a sheet formed of regenerated celluloseand having on its surface a multiplicity of particles of metal of atomicdimensions deposited in a layer having a granular structure, but givingthe visible appearance of a continuous, lustrous coating, said layer ofmetal particles having the property of following the expansion,contraction and wrinkling of the sheet material without cracking orflaking off.

5. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of a non-fibrous, organic, plasticmaterial swelling in water and having on its surface a multiplicity ofparticles of metal of atomic dimensions deposited in a layer having agranular structure, but giving the visible appearance of a continuous,lustrous coating, said layer of metal particles having the property offollowing the expansion, contraction and wrinkling of the sheetmaterial-without cracking or flaking off, said metallized sheet having acoating of a moistureproof, transparent composition.

6. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of regenerated cellulose and havingon its surface a multiplicity of particles of metal of atomic dimensionsdeposited in a layer having a granular structure but giving the visibleappearance of a continuous lustrous coating, said layer of metalparticles having the property of following the expansion, contractionand wrinkling of the sheet material without cracking or flaking oil,said metallized sheet having a coating on both sides of a moistureprooftransparent composition.

7. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of a non-fibrous, organic plasticmaterial and having on its surface a multiplicity of particles of metalof atomic dimensions deposited in a layer having athickness of notsubstantially greater than .0002 of an inch and having a. granularstructure but giving t .e visible appearance of a continuous lustrouscoating, said layer of metal particles having the property of followingthe expansion, contraction and wrinkling of the sheet material withoutcracking or flaking off.

8. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of a non-fibrous, organic plasticmaterial and having on its suruface a multiplicity of particles of metalof atomic dimensions deposited in a layer having a granular structurebut giving the visible appearance of a continuous lustrous coating, saidlayer of metal particles having the property of following the expansion,contraction and wrinkling of the sheet material without cracking orflaking off, said sheet material being colored with a substance capableof absorbing light transmitted by the layer of metal particles.

9. As an article of manufacture, an insulator against light and thermalradiation comprising a sheet formed of regenerated cellulose and havingon its surface a multiplicity of particles of silver of atomicdimensions deposited in a layer having :3.

a granular structure but giving the visible appearance of a continuouslustrous coating, said layer of metal particles having the property offollowing the expansion, contraction and wrinkling of the sheet materialwithout cracking or flaking off; i

10. As an article of manufacture, an insulator against light and thermalradiation comprising a.

plurality of superimposed transparent sheets formed of an non-fibrous,organic plastic material, at least one of said sheets having on anenclosed surface a multiplicity of particles of metal of atomicdimensions deposited in a layer having a granular structure but givingthe visible appearance of a continuous lustrous coating, said layer ofmetal particles having the property of a following the expansion,contraction and wrinkling of the sheet material without cracking orflaking off.

PAUL ALBERT WICKMANN.

